Abstract
Over the past few years, a wide use of externally-bonded fiber-reinforced polymer composites (EB-FRP), for rehabilitation, strengthening and repair of existing/deteriorated reinforced/prestressed-concrete (RC/PC) structures has been observed. This paper presents a nonlinear iterative analytical approach conducted to investigate the effects of concrete strength, steel-reinforcement ratio and externally-reinforcement (FRP) stiffness on the flexural behavior and the curvature ductility index of the FRP-strengthened reinforced high-strength concrete (RHSC) beams. Analysis results using the proposed technique have shown very good agreement with the experimental data of FRP-strengthened/non-strengthened RHSC beams, regarding moment–curvature response, ultimate moment and failure mode. Also, a newly prediction equation for the curvature ductility index of FRP strengthened RHSC beams has been developed and verified. Then, converting equation of the curvature ductility index to energy one is proposed. Results indicate that the proposed predictions for the curvature and energy ductility indices are accurate to within 1.87% and 3.03% error for practical applications, respectively. Finally, limit values for these bending ductility indices, based on different design codes’ criterion, are assessed and discussed.
Highlights
Over the past three decades, rehabilitation, strengthening and repair of reinforced and prestressed concrete structures (RC, PC) by the external-bonding of fiber-reinforced polymer (EB-FRP) strips/sheets have become very popular around the world due to lots of interested advantages of FRP composites over other conventional materials
The first is to examine the effects of concrete strength, steel-reinforcement ratio and externally-reinforcement (FRP) stiffness on the flexural behavior and the curvature ductility index of the FRP-strengthened reinforced high-strength concrete (RHSC) beams
In order to verify the accuracy of the proposed analytical model, available experimental data on the flexural behavior of non-strengthened/FRP-strengthened RHSC beams are collected from the existing literature [4, 33,34,35,36,37]
Summary
Over the past three decades, rehabilitation, strengthening and repair of reinforced and prestressed concrete structures (RC, PC) by the external-bonding of fiber-reinforced polymer (EB-FRP) strips/sheets have become very popular around the world due to lots of interested advantages of FRP composites over other conventional materials. In 2015, Skuturna and Valivonis performed a statistical analysis of the design methods (e.g. ACI440.2R-08, fib bulletin 14, TR55) to calculate the load-carrying capacity of RC flexural elements strengthened with external CFRP reinforcement, based on the experimental results of 80 beams. The first is to examine the effects of concrete strength, steel-reinforcement ratio and externally-reinforcement (FRP) stiffness on the flexural behavior and the curvature ductility index of the FRP-strengthened RHSC beams. For this purpose, an iterative analytical technique is presented which considers: a) nonlinear behavior of materials by using basic models for complete pre- and post-peak stress-strain behavior of HSC and internal/external reinforcement (steel/FRP); b) occurrence possibility of FRP premature debonding mode. According to obtained results, limit values for bending ductility indices, based on codes’ ductility criterion, are assessed and discussed
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